The invention relates generally to reciprocating piston pumps for creating and delivering a continuous output or flow of ultra high pressure water to be utilized in water jet cutting operations, and more particularly to such piston pumps having means for cushioning the deceleration of each stroke, particularly as the change-of-direction of the reciprocating pumping member approaches. The apparatus of the present invention finds particular application in positive displacement pumps utilized for intensifier applications, particularly those having high volumetric output or capacity. Pumps of this type are utilized in both mobile and fixed industrial applications, and may be utilized for such operations as coating removal, surface cleaning, water jet and abrasive jet cutting. The pumping apparatus of the present invention is particularly designed to function in a cushioning application for an intensifier utilized for water jet cutting apparatus operably adapted to generate and deliver water at ultra high pressure for delivery to a cutting head that discharges or delivers the ultra high pressure water as a high velocity jet for undertaking cutting operations on a workpiece. A high velocity jet of water into which an abrasive material is dispersed may be utilized for cutting workpieces fabricated from materials having hard and/or brittle mechanical properties, with these materials being otherwise difficult to cut or bore through conventional mechanical techniques.
While it is desired that intensifier pumps operate at high rates, it has been found that reciprocation rates are limited. One primary limitation imposed upon reciprocation rates is the rate at which impact occurs between the piston face and the end cap. Conventional intensifiers are limited to a maximum reciprocation rate or stroke rate of about 60 cycles per minute, this being the rate that impact may occur. When it becomes desirable to increase the volumetric output or capacity, conventional techniques would select either a larger displacement per stroke or increase the number of intensifier units. The present invention provides an additional solution in that a cushion design is provided which helps decelerate the piston as it approaches the point at which it changes direction of travel. With the improved cushioning apparatus of the present invention, intensifier apparatus have been found to perform more smoothly and at higher reciprocation rates, with a typical maximum rate being increased to a range of about 85 cycles per minute.